Flow cups are still the most important test instruments for the rapid determination of viscosity of liquids in the lab and in production processes. However, the flow cups are suitable only for low-viscosity liquids, but not for highly viscous substances such as pastes, etc. The most accurate results are obtained for liquids with Newtonian behavior. In that case, the flow cups take a certain volume of liquid that can flow out through a small opening. The result is expressed as time in seconds which is takes for liquid, till the first irregular flow occurs.